[unreadable] Transplantation of islets of Langerhans has long held promise as a cure for Type 1 diabetes mellitus. In the past, most islet transplants failed to achieve insulin independence. Recently, a new immunosuppressant protocol developed at Edmonton, Canada has significantly improved the success rate of islet transplantation. Nevertheless, there remain serious problems that negatively impact the outcome of islet transplantation. Reduced islet viability due to the trauma of isolation has made it necessary to use multiple donors to achieve insulin independence in a single recipient. The loss of supporting cells and extracellular matrix also contributes to transplant failure. Some progress has been made in addressing these problems by culturing islets in vitro before transplantation, allowing some recovery of islet viability. In this application, we propose to use a new culture technique employing a simulated microgravity bioreactor developed at NASA to dramatically improve islet culture and thereby increase islet viability after transplantation. The specific aims of phase I are: 1. To construct a modified perfused Rotary Cell Culture System (RCCS) to maintain islets in a carefully controlled physiological environment to improve viability. (a) Use automated media changes to maintain physiological pH and glucose levels. (b) Use automated infusions of growth factors and other biochemical agents to help sustain normal islet function. 2. To assess in vitro islet structure and viability in the RCCS compared to conventional static culture. (a) Structural integrity assessed by immunohistochemistry. (b) Function assessed by secretagogue-stimulated hormone secretion. (c) Viability assessed by a battery of assays. After optimization of islet culture in the perfused RCCS using rat islets in phase I, the procedures will be applied to human islets in phase II and tested in an animal model of diabetes. [unreadable] [unreadable]